Teachers’ unions are on the defensive, writes New York Times columnist Frank Bruni. Hollywood’s upcoming Won’t Back Down — heroic mother teams with idealistic teacher to take over a low-performing school — shows how negatively teachers unions are viewed, he writes.

“When did Norma Rae get to be the bad guy?” asks a union leader (Holly Hunter) in the movie. I don’t know, but that’s indeed the state of play when it comes to teachers’ unions, and it’s a dangerous one.

The parents Bruni knows are draining their bank accounts to pay private school tuition, but most families can’t afford it. Ninety percent of children attend public schools.

The teachers’ unions are unhappy with President Obama’s education secretary, Arne Duncan, writes Bruni. They don’t like the policies promoted by Race to the Top. At the local level, top Democrats are bucking the unions.

In Chicago, Philadelphia, Los Angeles and other cities, Democratic mayors have feuded bitterly with teachers’ unions and at times come to see them as enemies. And at a meeting of the United States Conference of Mayors in June, Democratic mayors joined Republican ones in a unanimous endorsement of so-called parent trigger legislation, about which unions have serious reservations. These laws, recently passed in only a few states but being considered in more, abet parent takeovers of underperforming schools, which may then be replaced with charter schools run by private entities.

Teachers’ unions have hurt their reputations by defending teachers’ tenure and seniority rights without regard to the welfare of their students, writes Bruni. “We were focused — as unions are — on fairness and not as much on quality,” American Federation of Teachers chief Randi Weingarten conceded in a phone interview.

The unions have also run afoul of the grim economic times. “In the private sector, nobody’s got any security about anything,” said Charles Taylor Kerchner, a professor of education at Claremont Graduate University. So the unions’ fights over pay raises and pensions, he said, made previously routine negotiations “look like pigs at the trough.”